The present invention is directed toward medical catheters and leads generally, and more particularly is directed toward mechanisms for introduction of leads and catheters into the human body.
Introducers and guide catheters are widely employed to place indwelling electrode leads and catheters in desired locations within the body. These devices typically take the form of elongated tubular sheaths, which may be straight or curved in configuration, through which the lead or catheter to be placed is advanced. Examples of introducers employed to facilitate entry of leads into the vasculature are disclosed in U.S. Pat. No. 4,166,469 issued to Littleford and U.S. Pat. No. 5,409,469 issued to Schaerf et al. Introducers or guide catheters of substantially greater length, provided with pre-formed curvatures or deflection mechanisms to facilitate locating the tip of a lead or catheter after it has been substantially advanced into the vascular system of a patient are also well known. Examples of such guide catheters are disclosed in U.S. Pat. No. 4,195,637 issued to Gruntzig et al. and U.S. Pat. No. 5,868,700 issued to Voda et al. An alternative mechanism for directing an indwelling electrode lead or catheter is to provide a two-piece structure including inner and outer tubes which may be moved relative to one another to provide distal sections with controllable adjustable curvatures.
The present invention is directed toward an improved deflectable tip introducer or guide catheter (hereafter referred to as an introducer) optimized for placement of leads or catheters within the vasculature of the human body. In particular, the introducer is optimized for placement of leads in the coronary sinus.
The improved introducer is a two-piece structure including inner and outer concentrically located tubular sheaths, in which the materials of the sheaths are particularly optimized to provide high torque and pushability while providing a minimal cross-sectional area of the wall. The inner and outer sheaths are preferably provided with different curved configurations, so that the over-all displayed curvature of the introducer over its distal portion may be adjusted by longitudinal movement of the inner and outer sheaths relative to one another.
In a preferred embodiment, the inner sheath may have a structure corresponding to the body of a conventional guide catheter, for example, corresponding to the SHERPA(copyright) guide catheters sold by Medtronic, Inc. Exemplary structures of similar catheters are disclosed in U.S. Pat. No. 5,755,704 issued to Lunn, U.S. Pat. No. 5,545,149, issued to Brin, et al. and U.S. Pat. No. 5,811,043 issued to Horrigan, et al., all incorporated herein by reference in its entirety. The inner sheath of the introducer may also have a structure corresponding to guide catheters of other types, marketed by Bard, Guidant, Boston Scientific, Cordis, or the like, for example, as disclosed in U.S. Pat. No. 4,863,442 issued to DeMello, et al, U.S. Pat. No. 5,921,952 issued to Desmond III et al., or U.S. Pat. No. 6,061,588 issued to Thorton et al. Typical materials employed for such guide catheters include polyurethanes, polyethylenes, polyesters, polyether block amides, polyamides, polytetrafluoroethylenes and the like, reinforced by polymeric or metallic braids or wires. Alternatively, the inner sheath may take the form of an un-reinforced tube of any of the materials referred to above.
The outer sheath is preferably fabricated of a thin tube of polyetheretherketone (PEEK) polymer (VICTREX(copyright) 381G or VICTREX(copyright) 450 manufactured by Victrex PLC.) or other material having a relatively large stiffness as compared to the inner sheath. The outer sheath is sized to fit closely (e.g., about 0.007 inches or less total clearance) around the inner sheath, and has a thin wall (e.g. about 0.005 inches in thickness or less). If it is desirable to utilize a slitting tool to remove the outer sheath before the inner sheath after the delivery of the therapeutic or diagnostic device, the clearance between the inner and outer sheaths should not be reduced substantially below 0.020 inches. A PEEK tube of this type, while providing for good torque transfer along its length, would normally not be suitable as an introducer sheath due to a tendency to kink when twisted or bent. However, when supported by the inner sheath, the outer sheath of PEEK tubing, in spite of its thin walls, serves admirably to assist in transfer of torque along the composite introducer assembly and in conjunction with modification of the curved configuration displayed by the distal end of the introducer assembly as a result of relative longitudinal movement of the inner and outer sheaths.